Digital Flight Control Systems for current and future generation high performance fighter aircraft require highly precise air data i.e., angle of attack and sideslip angle, for closed loop control of aircraft attitude and flight path. Conventional equipment used to provide these data has several disadvantages, among which are the following:
(1) heating is required for de-icing probes that measure pressures; PA0 (2) extensive pneumatic plumbing is required; PA0 (3) measurements can be adversely affected by engine power changes; PA0 (4) external probes and in-flight damage and create aerodynamic drag; and PA0 (5) pressure measurements tend to be inaccurate at high frequencies, i.e. during flight maneuvers or in the wake of another aircraft.
Accordingly, it is the object of the present invention to provide a method for developing the required air data which obviates these disadvantages.
In order to satisfy the aforenoted object of the invention, angle of attack and sideslip angle are first developed relative to inertial space and then in accordance with aerodynamic force equations. The data so developed are blended so that the data developed relative to inertial space are used at high frequencies such as occur during the aforenoted flight maneuvers or in the wake of another aircraft, and the data developed in accordance with aerodynamic force equations are used at low frequencies.